Contrary to what some promoters would have you believe, forming a corp or LLC doesn't magically turn ordinary expenses into deductions. LLC's/Corps are useful tools and I advise clients to form them in many cases, but forming a business and deducting expenses doesn't require a corp or LLC.
The expenses described by Mike above are all available without an LLC, but do require a business. Having a business on the side does allow me to make largely tax free income from the side business due to the deductions against the income.
The examples I listed are available to sole proprietorship's, that is true.
However, LLC's aren't that expensive and are generally considered the least expensive to form and keep up. However that is state to state and person to person in determination of cost.
My businesses are both service industry related, not real estate. I still prefer LLC for the amount of income I bring in. But these are my primary sources of income, not a side gig.
And LLC's are usually pass-thru when it comes to taxes, however you can elect members and managers and make yourself a manager and then deduct your salary from income if you elect someone else to be a member, like your spouse.
You can opt to be treated like a CORP via IRS Form 8832. After electing corporate tax status, an LLC may further elect to be treated as a regular C corporation or as an S corporation.
Personally I have elected my LLC to be taxed as an S-corporation which I feel has the best possible small business structure for taxes. It combines the simplicity and flexibility of an LLC with the tax benefits of an S-corporation which amount self-employment tax savings.